Apparatus for seismic surveying



Feb. 6, 1945. E. M. sHooK ETAL APPARATUS FOR SEISMIC SURVEYING 8 sheets-sheet 1 Original Filed March 20, 1940 Feb.

E. M. SHOCK ETAL APPARATUS FOR SEISMIC SURVEYING Original Filed March 20, 1940 8 Sheets-Sheet 2 GAL Vif/0Min?? Feb. 6, 1945. E. vM. sHooK Erm. 2,369,082

' APPAATUS FOR sEIsMIc sURvEYING Original Filed March 20, 1940 8 Sheets-Sheet 3 Feb. 6, 1945. y f E. M. sHooK ETAL 2,3b9082 APPARATUS FOR SEISMIC SURVEYING original Filed March 2o, 1940 8 Sheets-Sheet 4 Powie mc/r Fehao 6, 1945. E. M. sHooK E-rAl.

APPARATUS FOR SEISMIG SURVEYING 8 Sheetsf-Sheet 5 Original Filed March 20, 19404 AUAAIAAAAAAA NEYNDQQS E Feb 6 945v E. M. sHooK.- ETAL 2,369,082

APPARATUS FOR SISMI SURVEYING original Filed March 2o, 1940 '8 Sheets-Sheet 6 I-l-tra-lillw'llllll @www Feb. 6, 1945.

E. M. SHOOK ETAL APPARATUS FOR SEISMIC SURVEYING Original Filed March 20, 1940 8 Sheets-Sheet '7 lll A A l Feb. 6, 1945.4 E SHOQK HAL 2,369,082

APPARATUS Foa sEIsMIc suRvEYING original Filed March 2o, 1940 8 sheets-Sheet 8 UPHLE BPA-AA UPHOLE gmc/Mien Patented'Feb. 6, 1945 APPrRATUS FOR'SEISMIC SURVEYING- Earley M. Shook and Robert W. Olson, Washington, D. C., assignors, by mesne assignments, to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Original application March 20, 1940, Serial No.

324,930, now Patent No. 2,340,275, dated January 25, 1944.

Divided and this application March 12, 194s, serian No. 478,944

' 14 claims. :(01.17'7-352) This application is a division of our copending application Serial No. 324,930, filed March 20,

1940, now Patent No. .2,340,275 dated January 25, 1944.

This invention relates to `apparatus for recording seismic waves and more particularly to apparatus for recording the "instant of detonation of a charge of explosives which creates seismic waves in the earths surface and means.for automatically disconnecting a detector or geophone that is used to detect vertically traveling disrupting the process ofl recording seismic waves in the manner which has been practiced heretofore in the art of reflection Vseismic survey.

In the art of seismic prospecting, it has heretoiore been necessary to provide means ywhich will respond to an electrical impulse for producing an indication of the instant of detonation of an explosive charge. This indication when recorded on a seismogram is known in the art as the time break. To produce such a time break with some forms of apparatus known it is necessary that reliance must be placed upon an operator for properly connecting the circuits which detonate the charge of explosive. With this particular type of apparatus if the detonator for the explosive charge has been improperly connected, the rupture of the detonating circuit will produce a transient voltage that is of a polarity that will not be transmitted through the apparatus to the recorder. This would result in an erroneous time break that would come from subsequent impulses which have been `generated by making and breaking the detonating circuit after the charge of explosivcs has been detonated. By theinstant invention it is possible to eliminate these diiculties by providing suitable circuits whereby, regardless of the polarity f the transient voltage generated in the detonating circuit, the rupturing of the detonating circuit will produce an indication on the seismogram that is being recorded which will be accurate and .a true indication of the instant of detonation oi the explosive charge,

In addition tothe time break circuit described above, a number of other circuits by means of which the instant of detonation can-be registered on a seismogram are known. Some of these do not discriminate asa to the polarity of the electrical impulse whichindicates 'the instant of detona-l tion. Although these circuits 'do not have pclarity discrimination they have not proven entirely'satisfactory due to the fact thatl no means have been provided for eliminating spurious voltages which when recorded on a seismogram would appear as time breaks. These objectionable features `have been overcome by the instantinvention. l.

When conducting ,a seismic survey of a particular area it is always necessary that consideration be taken of the weathered unconsolidated stratum oi the earths surface for in this stratum the velocity of wave travel is considerably less than the velocity of wave travel in the denser media. If one fails to take cognizance of this fact, errors are introduced in both the correlation and thesubsequent proles computed from the data for this particular area. Therefore, this invention further contemplates apparatus for recording data from which the Velocity of vertically traveling waves in the unconsolidated outermost stratum of the earths surface can be determined.

The instant invention further provides circuit arrangements whereby one geophone that has been placed adjacent the mouth ofthe shot hole, known in the art as 'the uphole geophone, can be disconnected from the circuit of a geophone forming apart of the standard spread or rendered inoperative after it has detected the first direct traveling impulses. In other words, means are provided whereby there can be recorded on` a v single trace of a multiple-trace seismogram the time break, the first break or breaks arriving at the uphole geophone, the rst break of a geophone in the conventional spread and subsequent waves comprising refracted and reflected Waves which are detected by this geophone. A conventional spread such as that referred to in this" application is of thetype used in reflection or refraction seismic surveying, that is, the geophones/are collaterally spaced from the shot point.

From the above it is obvious that the diiiiculties encountered' by those practicing the methods of 'theprior art are obviated in that all the data that is necessary from a'single spread when shot in one direction can be recorded on a single seismogram. This record will include a timev break indicative of the instant of detonation of the explosive charge which creates the seismic waves in the earths surface, the time consumed bythe vertically traveling waves from thel explosive charge to the surface and the time required for these waves which have been created by the explosive charge to travel downwardly to the inl ierfaces of the subsurface strata and be reflected back to the geophones which have'been collaterally spaced from the shot point.

Reverting to the phase of the instant invention which provides for accurately recording the instant of detonationof the explosive charge which creates the seismic waves in the earths surface,

the error due to the human element involved is :completely eliminated in that regardless of the manner in which the detonating circuit is made up, the transient voltage resulting from the cure rent dying out of the detonating circuit will always initiate the operation of means which will mark the exact instant of the detonation of the explosive charge. This feature of the invention forms the subjects matter of our divisional application, Serial Number 478,943, filed March l2, 1943, and entitled "Apparatus for transmitting seismic signals.

Another feature of the instant invention residesv I in the provision of novel means whereby the indication of the instant of detonation, the time break impulse, as well as the rst impulse from the uphole geophone can be communicated from the shot point to the recording apparatus by means of telephone or radio. The local terrain of a particular area in many instances makes the use of telephone lines or conductors very impractical, particularly when the survey is-being conductedlon bodies of water, such as lakes, or in swamps. I

Therefore, a primary object of this invention scription when considered in connection with the drawings in which:

Figure 1 is a diagrammatic illustration of a circuit by means of which the time break impulse y regardless of polarity can be transmitted to the recording unit by means of telephonie communication Figure 2 is a diagrammatic illustration of an electrical circuit which differs from that shown in Figure 1 in that the system is connected by vcapacitauces to the telephonic communication system;

Figure 3 is a diagrammatic illustration of a circuit byv means of which uthe time break can be communicated to the recording vunit showing the push-push time break circuit located at the recording end of the telephoneline;

Figure 4 is a modiication ofthe. circuitshown in Figure 3;

Figure 5 is still another modification of this circuit;

Figure 6 is a composite wiring diagram of electrical circuits by means of which voice communication can be had lbetween the shot firer and the recording instrument operator, means forl communicating the time break impulse to the recorder and means for communicating the iirst impulse from the uphole geophone to the recorder;

-Figure 7 is a modiiication of the circuit diagram shown in Figure 1 differing therefrom in resides in the provision of apparatus for accurately producing on 'a seismogram an indication of the exact instant of detonation of an explosive charge that is used to create seismic waves in the ea'rths surface.

Another object of this invention resides in the I travel vertically from the explosive charge have been detected; Y

It is still a' further object of this invention to provide means lfor automatically rendering inoperative the uphole geophone after the vertically traveling waves have been detected and prior to the reception of waves which have traveled digeophone-to the recording equipment by means of a single telephone or radio communication channel. A

Still another object of this invention resides in the provision of means whereby a plurality of data can be recorded on a single trace of a seismogram in such a manner that any one datum will not interfere with the other data.

` rOther objects and advantages of this invention will'be apparent from the following detailed devthat the time break impulse is communicated to the recorder by means Aof radio; g

Figure 8 differs from Figure 'l in that circuits are provided whereby the first impulses received by the uphole geophone are also communicated to the recorder by means o1' radio:

Figure 9 is a modification of the invention illustrated invFigure 8. By means of, the circuits illustrated in this diagram the same data can be communicated by radio to the recorder;v

Figure 10 is a'wiring diagram of an electrical .circuit of another modiiication of this invention -by means of which the time break and the uphole geophone impulses can be communicated to the recording instrument; f

Figure `11 is illustrative of a seismogram which has been recorded that shows the time break, secondary breaks such as those produced by making and breaking rof the' detonating circuit after `detonation occurs and rst breaks suchas those received by any one of the geophones of thev spread on one trace and the uphole geophone impulse on the other trace;

Figure 12 illustrates a typical record of' the type recorded when using the invention forming the subject matter of this application. The im pulse corresponding to the uphole geophone sig' nal has rbeen recorded on a separate trace;

Figure 13 is an illustration of a single trace of a typical record whichhas been recorded when using the invention forming the subject matter of this application showing the time break, the uphole geophone impulses and the 'iirst break on the same trace of the seismogram in ,such a manner that anyone of the three will not obscure the other; and

Figure 14 illustrates one trace of a seismogram on which the time-break. the uphole geophone impulses, the iirst break. and subsequent reflections have been recorded.

Referring to the drawings in detail, in particular, Figure 1, there is shown a circuit diagram of one phase of this invention which deals with the communication of a signal, indicative of the instant of detonation of an explosive charge to create seismic. waves in the earths surface, to`

a recorder. By means of this electrical circuit a signal indicative of the true instant of detonation will be transmitted to the recording apparatus regardless of the polarity of the signal voltage generated when the blaster circuit is ruptured by the detonation of the explosive. The current dying out of the blaster circuit, illustrated by block diagram at I0, produces a transient voltage that will be communicated to the resistance by means of the conductors I2 and |3. Current flowing through the resistance II willproduce an instantaneous voltage drop across this resistance which serves as a charging potential for condensers I4 and I5. Condensers I4 and I5 are in the -grid circuit of the gas triode tubes I6 and Il. monly known by the trade name Thyratron Their characteristics are such that when a negative potential of suicient magnitude has been placed on their grids, by means of the battery |58, no plate current will flow. When this negative bias has been -removed or in part equalized, the gridwill lose control in the tubes and plate current will flow until it has been interrupted by some means. Therefore, a charging potential placed on condensers I4 and I5, depending upon its polarity, will cause one of the tubes I6 or |'I T hese tubes are of the type comphones are used with their respective amplifiers to fire, resulting Vin the flow of plate current y through resistance I9 or 20 to charge condenser 2|. The plate current in charging condenser 2| will produce'a voltage drop'across resistor 22.

. 'I'his voltage drop across the resistor 22 being iny the form of a pulse can be impressed ufpon the primary winding 23 of a transformer 24 to produce a corresponding signal in the secondary windings 25 and 25. By means of conductors 2l and 28 this transformed voltagerpulse is com-I municated to the communication runit 23 and conductors 3i! and 3| to the recording galvanometer 32, where it is recoded on a trace of the seismogram.

Tubes It and VI are provided with a common gridbias potential IS. By connecting these two charged, plate current can no longer flow in the circuit. Therefore, the second tube will be prevented from iiring on subsequent impulses which are of opposite polarity to the rst impulse received. The condenser 2| therefore in effect acts as a trap to stop the flow of plate current from the gas triodes I6 and I '5. -Additionally, after one of the gas triodes I6 or II has red, no further signals will be communicated to the recorder from the blasting circuit. This condition will exist until .condenser 2| has been discharged through the resista-nce 2 I This will eliminate spurious voltages generated by the detonating circuit and blaster` itself from beingI ondartv windingr of the transformer 2d is divided.

and the two sections 25 and 26 of the winding have connected in series with them. but between them. a microphone 33 and a receiver 3d. (Eonu through the communication unit, `by means of norneter 5l at the instant or rupturing of the Abe ageophone of a conventional spread. This geophone is connected by means of conductors 36 to the input of an amplier 31,.

The output of the amplier 3l is connected by means'of conductors 3 8 to the recording galvanometer 32.

In some, cases it is desirable to use the time break impulse received from the 'blaster circuit l to initiate the operation of a master control which controls the gain in amplification derived from one or more ampliers. When this is the case, the communication unit 29 is connected to the master control 39 by means of conductors 40. 'I'he master control then is appropriately connected "to the amplier through leads 4|. Al-

though forpurposes of explanation a single geophone 35 is shown in this figure, it is apparent to those skilled in the art that a plurality of geowhen doing reection seismic survey work.

In Figure 2 there is shown a slight modification Yof the circuit illustrated in Figure 1. The circuit of Figure 2 diiiers from that of :Figure 1 in that the plate circuit of the gas triode tubes I6 and I'I is capacitively connected by means of' condensers 42 and 43 to the conductors 2'I and 28 instead of by means or the `transformer 24 shown The microphone 33 and receiver 34 in Figure 1. in the circuit of Figure 2 are connected in series and across the leads 2l and 28 on the opposite side of condensers 42 and 43 from the resistance 22. This circuit functions in the same manner described in connection with Figure 1.

Still another modification of this invention is shown in Figure 3." In this instance the time break circuit is located not at the shot point but at the recording location. The impulse generated by the rupturing of the blasting circuit is communicated by means cf the telephone lines 2l and 23 to the resistance '44. This impulse regardless of its polarity produces an IR, drop across this resistanceV which acts as a charging potential for the condensers 45 and 46. The cur rent flowing in the circuit while charging con-l densers and produces an IR drop across the resistances drand 48. Depending upon the po-` larity of the impulse received from the blaster, the IR drop across one of the resistors 4l and 48, will'add vto the grid bias as supplied by battery t9 `on one of the gas triodes 50 or 5I to become sumciently less negative that one .of the tubes will iire` to produce a iiow of plate current through its respective resistance 52 or 53 to charge the condenser 5e. The battery 55 is the usual plate potential supply. Current owng in the plate, circuit while condenser 54 is becoming charged produces an IR drop across'resistance 56 which can be recorded directly on a recording galvadetonating circuit. Duplex communication can be had between the shot;l frer and the recording instrument operator by means of the conventional communication equipment through the conductors 58, 59, 27, and 28.

A further embodiment of this invention is illusi trated by the circuit diagram in Figure 4.- This circuit is intended .to transmit a signal that is indicative of the instant of detonation of the ex- Vgas triodes I6 or I1 to iire. 4the flow of current through resistors 41 and 48A geophonethat is placed adjacent the shot point. and speech by a singletelephone channel and at the same time prevent the three pulsations from interfering with one another or from causing in- Aplosive `charge, the rst impulse received by the terference on the record. The time break willbe transmitted withoutI polarity discrimination.

In this embodiment of the invention, the transient voltage produced in the detonating circuit of the blaster l0, in the manner described in connection with Figures 12 and 3, causes one of the This is caused by which will produce an IR drop across them. The IR drop across one o! these resistances will add to the bias potential supplied to one lof the tubes i lI6 or -IT by means of the battery 60 in such a way as to cause the grid to lose control and the tube to become conductive. Current iiowing in the plate circuit will be in the form of a surge that 'will charge condenser 6|.

This impulse is transmitted through the battery 62, the resistance '63, back to the cathodes of the gas triodes I6' and I1. The flow of this current through the resistance 63 will cause the grid potential on the grid of gas triode tube` 64 to become sufficiently l less negative that the gas triode 64 will becomel conductive and a current will 'ow in its plate circuit. Inductance' 65 is placed-inthe plate ciry -suil'icientlylong that the uphole` geophone will have ample time to detect the first impulseY of waves traveling vertically upward from the explosive charge. `This period of time is controlled by inductance 65 plus resistances 66 and l61 and by varying the position of the tap 68 on the resistance 61. The plate current having been cut oil from tube 69 after the impulse' received from uphole geophone 10 has been amplied, trans- I'he circuit can be reset by momentarily closing the switch 90 permitting the condenser 6| to be dischargedthrough the resistance 92 and momentarily opening switch 93 to break the plate cirf'` cuit of the gas triode 64.r

vIn Figure 5 there is shown a modification of the circuit illustrated in Figure 4. The same results namely. the transmission of the time break, the

rst impulse from the uphole geophone, and tele` phone communication, can be transmitted over a vsingle telephone channel.- This circuit, like the one shown in Figure 4, will transmit the time breakl without polarity discrimination. The rst part of this circuit from the' blaster through the .two gas triodes I6 and I1 is identical with the Vvcircuit described and shownnin Figure 4. VThe current from one of the gas triodes |6 or I1 will flow through the conductor 94, the milliamxneter 95, the battery 96, the resistance 91, the conductor 98, backv to the cathode of the gas triode I6 or I1. resistance 91 produces an IR drop which will cause the bias potential supplied to the grid of -gas triode 99 to become less negative to cause triode 99 to re. The rst impulse of plate current owing from gas triode 99 through condenser A|00 will be impressed on the grid of an amplier tube |0I. The amplied impulse will be .transformed by the transformer |02 and conducted by means of the telephone lines |03 and` |04 to the recording galvanometer where it is,

. recorded on one of the traces of a seismogram.

. Resistancey I05is a coupling resistance. The flow of plate current from gas triode- 99 will also be |01 serves as .a gridbias for amplier. tube |0I.

through a portion ofthe resistance |06 to charge the condenser |01. The time required for condenser,Y |01 to become fully charged is controlled by the position of the contacter on resistance The fully charged potential of condenser When this' condenser reaches full. charge. the bias placed on the amplifier tube I 0I is suilicient l to entirely block it to prevent any further signals formed by the transformer 1| and communicated to the recording instrument by means of the conductors 12 and 13, no further signals can be communicated to the recording instrument and the same trace on which the time break and uphole geophone impulses were recorded can be used to record signals from one of the geophones in the conventional spread. Additionally, since the tube 69 isolates the blaster, the time break and uphole geophone circuits from the telephone 4line and recordingginstrument, noises 'such Vas.

those produced by the microphone 14 which is v, connected in the cathode circuit of tube ,69.wil1 f not produce disturbances on the trace of the seismogram. 1n order to receive voice signals from the operator of the recording instrument over the telephone line formed by'conductors 12 andy '|3,

from the uphole geophone orv from the blaster cir cuit from being conducted to the recording in strument. The period of timef required for condenser |01 to reach its full charge is controlled in such a manner that an impulse delivered to the uphole geophone by vertically traveling seismic waves can be amplied and transmitted to the recorder before ampliier tube |0| is biased to cutoff. By blocking amplifier tube |0I, the same trace on which the time "break and uphole impulses have been recorded can be used to record signals generated by one of the geophones in the conventional spread. All three signals will be recorded ona single trace without any one in- ,terfering with theV other.

The microphone 14 and telephone receiver 15.'

are connected in this circuit in the same manner as described in connection with thecircuit diagram of Figure 4. v-

A further modification of -this invention is shown in detail by the circuit diagram of Figure 6.

By means of this circuit the signal indicative of` the instant of detonation of the Aexplosive charge which produces seismic waves, the tlrst impulse generated by the uphole geophone. and signals generated byv a geophone of the conventional spread can be recorded ona single trace without one interfering with either of the others. This circuit like the others described above does not have a polarity discrimination characteristic. that is, the first impulse received from the blaster circuit or from the uphole' geophone whether The flow of this plate current through the c positive or negativewiu be transmited to the krecording apparatus and recorded on a trace of I the seismogram as true indications of the exact instants at which theyoccur.

A signal from the detonating circuit of the blaster is impressed across the primary Winding |09 of the transformer ||0. The resultant voltage in the secondary winding |I| of this transformer is connected through condensers 46 and 45 tothe grid circuits of gas triodes 6 and |1. This voltage will cause an IR drop to be builtup across the resistances 41 and 48 due to current flowing through them. One of these 1R drops` depending .upon the polarity of the impulse received from the detonating circuit of the through resistances |34 or |35 and plate /circuit blaster willfbe positive relative to the negative grid potential existing on the tubes I6` or |1.

' This positive potential causes the grid potential on one of the tubes t0 become less negative permitting the tube'to iire causing a now of current` in its plate circuit to charge condenser 6|. The flow of the current in the plate circuit of this gas triode will be in the form of apulse for whenA the condenser 6| becomes charged no further plate current can flow andas a. resultsubsequent signals from the blasting circuit will not fire the ,other gas triode. The pulse of current flowing to charge condenser 6| is transmitted by means of conductor l2 to the double pole double throw switch ||3 through the switch when it is thrown in an up position, and the conductor ||4, through resistor |31, meter 38, resistor |38 to ground and plus 75 volts, through D. C. supply to zero volts and back to the cathode of gas triodes I6 and |1.V This pulse of current causes |36 which is common to both of the gas triodes. This plate' circuit includesthe conductor |36, vthe resistor |31, the milliammeter |38, resistor |38 to ground and plus 75 volts, through plate supply to zero volts and to cathodes of'gas triodes of tube |21 and |28. The flow of plate current in this plate circuit through resistance |31 will produce a voltage drop which serves as a bias potential for the grid of amplifier tube |5. A At the instant the plate current begins to ow the impulse of the current building up in this circuit an IR drop across resistor |31, meter .|38 and j plus 75 volts D. C. by conductor |45 through the cathode resistor to the cathode of tube ||5. 'I'he Voltage induced in the secondary Winding |2| of this transformer is impressed on the telephone channel that is formed by the conductors 12 and 13.' 'Ihe signal is thus transmitted to the recording galvanometerwhere it is recorded on one of the traces of the seismogram as a true indication `of the exact instant at which detonation of the explosive charge occurred.

After the explosive charge `has been detonated 'seismic waves will travel vertically from the point where the explosion occurred to the surface of the earth where they are detected by a geophone |23 that has-been located adjacent the mouth of the shot hole. Since only the rst impulse detected by the geophone is used by the interpreter of the seismogram no more of the'signals generated by the geophone' are transmitted to the recorder and recorded. Therefore, means are provided as shown in the circuit diagram of Figure y6 for suppressing or completely eliminating all signals from the uphole geophone after the iirst impulse has been communicated to the recording instrument. 1 i

The rst impulse detected by the geophone |23 is communicated by means 'of the'transform.. er |24 to the grid |25 of ank amplifier tube |26. The ampliiier tube |26 amplifies this impulse and communicates the amplined signal to the grid is transmitted through the amplifier tube, conductor ||6 and contact ||1 of switch |8, transformer |20 and the telephone line formed by conductors 12 and 13 to the recording" galvanometer whereit is recorded on a trace of the seismogram. Since the plate current flowing. through the resistor' |31' builds up to its maximum immediately, the IR drop across this resistlance will bias the amplifier tube 5 to cut-off thereby blocking any further signals which would tend to pass through the amplier tube. This in effect isolates the recording instrument from the blaster, uphole geophone, and microphone circuits so that they willl not produce disturbances on the trace on which the uphole impulse and time break impulse have been recorded that would tend to obscure subsequent signals that are being recorded from a geophone in the conventional spread. Becauseof the characteristics of gas triodes, plate current will continue to lflow through resistance |31 and milliammeter |38 until the circuit has been broken. This can be accomplished by operating switch |51. This 0peration opens contact |59 which breaks the plate circuit for the gas triodes |21 and |28 and also closes contact |58 and thus discharges condenser 6| through resistance |50'. Switch |51 can be of the push button type in which the contacts |58 and |59 are resiliently biased to the position shown in the drawings.

When the contact arms |46 oigang switch ||8 are inthe positionshown in the drawings, voice communication can be carried on between the. recording instrument operator and the shot rer by means of the telephone receiver |41 and the microphone |43. The voice signals are .applied to the tube ||5 through a circuit whichmay be traced from one side of the batteryl |42, through the microphone |43, by conductor |44 to one side of resistance |38', by conductor |38 from the otherside thereof, contact |40, one 0f the arms |46 of switch H0, and by conductor |4| to the other side of the battery |42. However, when the contacts 46 of gang switch ||8 are thrown to theiruppermost position the microphone |43 is cutout of the circuit andan amplifier with a loud speaker is thrown into the circuit in such lamanner that the recording instrument operspeaker are then energized. Voice signals transmitted through the telephone channel or lines 12 and 13 appear across the winding I I9 of transformer |26, and are applied to the input circuit of amplifier tube |49. This circuit may be traced from one side o f transformer winding I|9 by the upper arm |46 of switch |I8 and by conductor I48a to the control grid of tube |49. The return circuit from the cathodeincludes a bias resistance and one of the switch arms |46 which leads to the other side of winding i9.

The device is shown as operating in conjunction with a vibrator power pack. The low volt.

A of thetubes through a circuit which includes the switch arm |48 ofswitch H6. The high voltage from the power pack supplies the entire plate and bias voltages, the voltage being taken from appropriate taps of a voltage divider 256.

When the uphole'geophone is not used the uphole geophone circuit can be disconnected from the remainder of the circuit by throwing the double pole double throw switch I|3 to its down position. This operation disconnects the filaments from'all of the tubes in the uphole geothe'plate circuit of gas triodes |6 and I1. This allows the time break gas triodes I6 and I1A to bias the repeating tube lI I5 to cut oil". 'I'hisfeadisconnected from it. For this purpose a spring biased switch |66 is provided which will cause the voltage circuit to the microphone to remain open except when manually held closed.

Battery |66 provides the plate potential for the 'preamplifier tube |63 as well as the plate potential for the gas triodes I6 and I1. When it is desired to reset the circuit it is necessary that the switch |16 be momentarily closed so that the condenser will discharge'through the resistor I 1I. Switch 9| is provided so that the negative potential can be removed from the grids of tubes |6 and I1 and causes plate current to ow for test purposes. The resistance |12 is placed in series with battery 60 to prevent shorting the battery when the switch 9| is closed.

In Figure 8 there is shown still another embodiment of this invention which is a modication of the circuits shown in Figures 7 and 6. This circuit includes the necessary apparatus for disconnecting the uphole geophone after the iirst impulse generated by it has been recorded on a trace of the'seismogram. The transmission of the time break and the uphole geophone impulse in this instance ls by means of radio.

' l In the manner described in connection with Figures 6 and 'l the impulse generated in the detonating circuit of the yblaster |0 is communicated to thegrid circuits of the gas triodes I6 and I1 to. initiate the ow of plate current from one ture is provided so that the shot rer will havey to reset the gas triodes I6 and I1 in order to talk 40 63 while condenser6| is being charged produces to the recording operator. I

Another embodiment of this invention is shown' by the circuit diagram in Figure '7. This embodi-r ment differs lfrom those described above in that the time break is transmitted-by radio rather than by telephone lines to the recording instrument without polarity discrimination. The sig: nal from the detonating circuit of blaster III is connected in the manner described above to the grid circuits of gas triodes I6 and I1 and in the same manner causes one of the tubes to re and charge' condenser 6|. Duringthe time the condenser 6| is being charged current will flow through resistance |6| in returning to the cath- ,a odes of either tube I6 or I1 and will produce an ier tube |63 can be adjusted by means of the variable tap |62 on resistor |6I. y

In order that the shot rer can communicate by voice with the recording instrument operator a microphone |66 is connected as shown to they primary winding of the'transformer |61', the secondary winding of this transformer being connected through the variable resistance |66 to the Y Ygrid circuit of the preamplifier tube |63. In this instance it is preferable to use a microp one of the type whose voltage potentialV |61 is normally of these triodes |6 or I1, dependent upon the polarity of the impulse received in the grid circuit. -In a similar manner the plate current will ilow from one of these triodes to charge the condenser phone ,circuit and eliminates condenser 6 I from 35 6|, The remainder of the plate circuit is the con-- ductor |16, milliammeter |14, the battery 62, potentiometer 6I, and the conductor |14a, which leads to the cathodes of the gas triodes I6 and I1. The ow of current through variable resistance an IR drop which '-.when algebraically added to.

the potential of the' grid bias battery 66 will cause the negative potential on grid |16 of gas triode |16 to become sufciently less negative that tube |16 will nre. The current from the plate of this l tube will build up slowly in the plate circuit due to the inductance 66 and the reslstances 66 and 61. This period of time is made variable by makingV the resistance 61 a potentiometer. By moveter the rst impulse detected by it is eiiected before the pre-ampliier tube |63 has been rendered inoperative to transmit signals. The IR dro'p produced across the resistance 66 and that portion of potentiometer 61 between its lower end and the variable contact 66 will build up to a value which will bias the'preampliiier tube |66 to cutoil' and thereby block it so that signals other than the iirst impulse from the upholegeophone and time break signals can not be com- 'municated to the recording instrument. The preamplier tube |63 is connected in the manner described in Figure- 7 through a transformer |64 to a modulator circuit of a conventional radio transmitter, as by conductors 12 andA 1l. The

v microphone by meansof which theshot tirer can communicate 'withthe operator on the recording instrument is also connected in the circuit in a similar manner to that described and shown in Figure?. f

Still another embodiment of this invention is disclosed inFigure 9. 4The arrangement of the gas triodes |6 and I1 relative to the blaster ciring the contactor 66 ot the lpotentiometer 61 a charges condenser cuit,is the same as that described above. Plate current ows to charge condenser 6| located in the plate circuit formed by conductor |11, milliammeter |14, battery 62, resistance |18, conductor |19, and the cathodes of tubes |6 and |1.

This current will produce an IR drop across the resistance |18 which when added algebraically td the potential of battery |80 will cause the grid bias potential on grid of gas triode tube |16 to become suiciently less negative that tube |16 will fire to produce a iiow of plate current. Resistance 18| is providedv in the grid circuit of tubes I6 and I1 to prevent shorting battery |80 when switch |82 is closed for test purposes. Resistanc |83 is a conventional coupling resistance. The plate circuit of gas triode |16 is divided into ythree branches comprising in one branch the coupling resistance |83, in a second branch a condenser |84 and variable resistance |85 connected in series and in the third branch a variable resistance |86, condenser |81 ,and resistance |88 connectedin series. At the instant the gas triode |16 fires and plate current begins to ow, since condenser |81 and resistances |86 and |88 have a small time constant, condenser |81 will become charged quickly, after which current will no longer flow in the third branch of the plate circuit. This impulse of current which |81 produces an IR drop across the resistancel|86 and a portion of this IR drop is tapped oi and conducted by conductor |89through an uphole geophone |90 to the grid circuit of a preamplifier tube |63. The signal from the plate'circuit of tube |63 is communi' cated to the modulator circuit of a conventional radio transmitter through the medium of transformer |64, and transmittedv to the recording -in- -strument 4by radio where it is received and recorded on a trace of the seismogram. After condenser |81 in the third branch of the plate circuit of tube |16 has become charged and current ceases to ow in this branch, condenser |84 will be charged. The capacity of this condenser is selected such that the time required for it to become fully charged will be suiliciently long to permit the uphole geophone |90 to detect and transmit through the preamplier tube |63 the rst impulse received by it. As soon as the condenser |86 is fully charged, the charging potential as derived from resistance |83 isv effective in biasing the preamplier tube |63 beyond plate .i current cutol. By blocking tube |63, no further signals, whether from the microphone |66 or from the uphole geophone |99, can produce modulation. This permits the trace on the seismogram on which the time break impulse and the uphole geophone impulse have been recorded to be used to record signals detected by one of the geophones in the conventional spread without interference. The microphone |66 and transformer |61 are connected in such a manner that the shot i'lrer can speak to the operator of the recording instrument.

Another modification of Figure 6 is shown inL inl "tube 262, transformer v263, repeating tube 264, transformer 265 to the telephonelines 12 and/13.

The first impulse from the uphole geophone |23 after having been amplified by the tube 262 will be transmitted to the grid of gas triode 266 byl means of conductor 261 and condenser 268. This impulse will drive the grid of tube 266 less negative and vcause the plate of tube' 266 to conduct. This current flows through resistance 269, contact 210 of switch 21|, resistance 212, conductor 213, to plus '15 volts D. C., to 0-volts D. C., conductor 214,.resistor 215, and back to cathode of gas triode 266. This current Aproduces an 1li.- drop across resistance 215 which charges condenser 216 through resistance 211. The polarity of thevoltage of condenser 216 is such that it reduces the 'negative grid voltage of gas tube 218 as supplied by the voltage divider. When the potential of condenser 216 reaches a certain value the grid of tube 218 will lose controlV and the plate circuit of tube 218 conductscurrent through f quired for condenser 21,6 to become charged to the critical value for tube -218 is determined by f the capacitance of condenser 216 and value of resistance 211. Since the timeio'f arrival of the first energy is the desired information, the time constant is set so that tube 218 will trip or start conducting on the order of .01 to .02 second'after the first impulse has tripped gas xtriode 266. When the plate current of tube 218 flows through resistances 283 and 284 and meter 282 an IR drop exists across them. This IR drop is of such value and polarity that it will increase the negative biason the grid of repeater tube 264 to the point Where tube 264 will cease repeating and will, therefore, cut the followingpsignals from the uphole geophone |23 out. Additionally, it will prevent the shot flrer from speaking to the recording operator over the microphone circuit composed of microphone 285, battery 286, and resistor 284. This arrangement requires the shot flrer toreset the apparatus by closing push button switch 21| down; r l

When the uphole time is notdesired, switch 2,19 is` turned to off position. This cuts oifY the plate of tube 218 and shorts out condenser 6| With these changes made, the time break 'pushpush gas triodes I6' and I1 conduct upon the f arrival of anl impulse from the blaster and this current ows through meter 282, and resistances 284 and 283 which produces an IR drop that disables repeating tube. 264. As in the previous iristance reset switch 21| mustbe thrown in the down position to cut the current out of the meter 282 and resistors 284 and 283.

Under some conditions the gas triode tube is. subject to firing upon the sudden application of plate voltage, even though the grid bias and plate voltage are the correct values for non-con'- duction as specified by the manufacturer. The combination of switch 21|, resistor 28|, and condenser 281 is an arrangement whereby the voltage is gradually applied to the plate of gas triode 218. Switch 21| is spring biased to the positiony shown'in the diagram. The switch is opened l each signal is definite and can be accurately read charged. This charge is approximately equal to the plate voltage available for the plate of tube 218. When switch 21| is released, condenser 281 discharges through resistor 28| and produces an IR drop which is opposite to the plate voltage. At rst it is seen that the voltage reaching the plate of the tube 218-is very low. As the condenser 281 becomes discharged and its resulting discharge current IR drop in resistance 28| decreases, the voltage on the plate comes upto normal. The same results. are obtained in the plate current of tube 266,'by. means ofi condenser 288, contact 210 of switch 21|, and resistor 212. y

Figure 11 illustrates a typical record showing only two traces. Trace a has recorded thereon a time lbreak impulse and the rst breaks occasioned by signals which 'have' been generated by a geophone in the conventional spread. Trace l b shows only a record of the signals'which have been'generated by an uphole geophone which has been placed adjacent the shot hole. On trace fa there is shown a succession of secondary breaks which follow the time break impulse. These secondary breaks are due to signals developed in the detonating circuit after the detonation of the explosive charge and arecaused by making and breaking the detonating circuit by the ends of the conductors to which the electric blasting cap 'was connected coming in contact with each other or the casing of the shot hole. Additionally, it will be noted that there is ref corded on trace a at c, a high frequency wave` by the interpreter.

The trace shown in Figure 14 diers from that shown; in Figure 13 in that signals corresponding to reflected waves are also recorded on the same trace with the other three data. Thisr trace represents an ideal record for it has all of the data recorded on it that is needed from a particular spread when shot in one direction. It will be noted that' after the first break has been recorded from the geophone in a. spread, that the gain in ampliiication is suppressed to some predetermined minimum value and automatically expanded with time in such a manner that all of the signals corresponding to reilected waves are recorded with substantially the same amplitude. i l

Although this invention has been described in detail in connection with the use of hot-cathode i AThese are referred to as gas triodes.

control-grid type tubes commonly known on the market as types 884 and 885, it is'obvious to those skilled in the at that these triodes can be replaced by cold-cathode starter-anode type gas'triodes. 'Ihese are generally known on the market as OAI-G gas triodes. A shield is indicated in the gas tubes of Figure 6 and Figure V1|). They are in fact gas tetrodes, due to the additional element." These are of the RCA 205| type. The general characteristics of the gas triode and gas tetrode are the same..

We claim:

l. An apparatus for transmitting a time break impulse, the impulse from\an uphole geophone, and voice signals overa single telephone channel that comprises a time break circuit, an uphole geophone circuit and a voice communication circuit all .connected to a single telephone channel,

. means connected with said time break circuit for of l'ow amplitude. The signals which produced this wave also originate in the blasting` circuit Y and are caused by commutator ripple in the blaster itself.

the uphole geophone impulse and the ilrst break from-a geophone ,in the conventional spread on the same trace, it is necessary that the spurious .illustrated in Figure 1.2 can be recorded. On

trace d, there is shown a denite time break and a definite first break occasioned by signals Vldetected by a geophone in the conventional spread. The spurious voltages which' cause'secl, ondary breaks and commutator ripple have been entirely eliminated from the trace. -By comparing trace d with`trace e, it is obvious'that the recordof the uphole geophone impulse could be In order to record the time break,

generatinga voltage impulse coincident with the instant of detonation of an explosive charge to -create seismic waves inA the earths surface and for blocking signals generated in the circuit, subsequent to the rst' impulse, from the telephone channel; means-in the uphole geophone circuit for producing a voltage impulse coincident with the rst impulse detected by the uphole geophone,

means for communicating this voltage impulse to the telephone channel, means in Athe uphole geophone circuit for blocking signals generated therein, subsequent to the first impulse, from the telephone channel, and said last-named means also being in the voice communication circuit for blocking voice signals from said channel.

2. In an apparatus for transmitting a time break impulse, an uphole geophone impulse recorded on the same trace with the time break and the rst break occasioned by a, geophone in the conventional spread. v

In Figure 13 -there is illustrated a trace of a seismogram on which the time break impulse, the

uphole geophone-break' and the first break from.

' ageophone in the spread arel all distinctly recordedl on the same trace. It will be noted that 'Il geophonesubsequent to the rst impulse or imand voice communication si ls over a single pair of conductors, and having electrical means including a detonating circuit for detonating an explosive charge to create seismic waves in the earths surface and means connected with the detonating circuit for generating a voltage' impulse coincident with the instant ot detonation of the explosive charge, the combination oi' means Afor communicating said voltage impulse to said pair of conductors, a microphone, an uphole geophone, means for amplifyingand communicating the amplified signals from saidmicrophone and Vfrom said uphole geophone to said pair of conductors, ameans whose operation is initiated by said voltage impulse for blocking said amplifypulses will be blocked from said pair of conductors.

3. An apparatus for producing and transmitting a signal indicative of the instant of detonation of an explosive charge to create seismic waves in the earth, an impulse'received by a geophone placed adjacent to the point of detona.

tion of said charge, and voice signals over a single teiephone channel comprising in combination, means for generating an initial voltage impulse coincident with the detonation of the explosive charge, acontrol gas triode tube, a plate circuit for said tube, means for placing a negative bias potential on the grid of said gas triode tube, means operated by the initialv voltage impulse to cause the grid potential on the gas triode tube to become less negative whereby current will iiow in said plate circuit, an amplifying tube, a grid in said amplifying tube, means for transmitting the initial voltage impulse to said amplifying tube, for amplification therein, said last mentionedmeans including the geophone whereby signals received by said geophone may be transmitted to said amplifying tube for amplification therein, means for transmitting said amplified signals to said telephone channel, means including a microphone for impressing voice signals on said grid of said amplifying: tube, means operable, a sufficient time after said initial voltage impulse to permit the receipt by said geophone of waves generated by'said explosive charge and, upon the ilo-w of plate current in said control gas triode tube, to cut o the ow of plate current in said amplifying tube and to prevent the communication of furtherfsignals to said telephone channel,

4. An apparatus for producing and transmit- Iting a signal indicative of the instant of detonation of .an explosive charge to create seismic waves in the earth, an impulse produced by a geophone a control gas triode tube, a normally' negatively biased grid for said control tube, a plate circuit including an inductor and a resistor for said control tube, means operated by the initial voltage impulse to cause the grid potential on the gas triode tube to become less negative whereby current will iiow in said plate circuit, an amplifying tube, a grid in said amplifying tube, means including a microphone for applying voice signals to said grid, means for transmitting the initial voltage impulse to said amplifying tube, for amplication therein, said last mentioned means including thegeophone whereby signals received by said geophone may be transmitted to said amplifying tube for amplification therein, means for transmitting said amplified signals to said telephone channel, means operated by the flow of plate current across said resistor for biasing the grid of the amplifier tube suicie'ntly negative to cut off the fiow of the plate current in said amplifyingftube to prevent the communication of additional signals to the telephone circuit, whereby subsequent signals received at the geophone and sound picked up by the microphone are not transmitted to said telephone channel.

.5. An apparatus for producing and transmitting a signal indicative of the instant of detonation of an vexplosive charge to create seismic wavesin the learth, an impulse received by a geophone placed adjacent to the point of detonation of said charge, and voice signals over a single telephone channel comprising in combination, means for generating an initial voltage 1mpulse coincident with the detonation of the explobecome less negative to permit plate current to flow in the plate circuit, an amplifying tube, a'

grid in said amplifying tube, means including a microphone and said geophone for transmitting the voltage impulse produced by the current flow through said resistor to the amplifying tube for amplification therein, means forl transmitting the amplified signals to said telephone channel,

a control gas tube, a normally negatively biased grid for said control tube, a plate circuit including an inductor and at least one resistor for said control tube, means Aoperable upon the flow of Icurrent, in the plate circuit of said first gas triode tube to cause the grid potential on said control tube to become less negative whereby current will ow in the-plate circuit of said control tube, means operated by the flow of plate current in said control tube plate circuit for biasing the grid of said amplifying tube more negative to cut oi theflow of plate current in said am:- plifying tube to prevent the communication of additional signals to the telephone channel.

6. In a system having a seismic Wave generating means and a geophone at a first location and at least one geophone and a recorder at a second location spaced a substantial distance therefrom, the combination of an amplifier at one of said locations having an input circuit and an output circuit, means included in said input circuit for producing an electrical impulse coincidentally with initiation by the generating means ofA seismic waves, means included in said input circuit and operable in response to arrival of seismic Waves at said geophone at said first location for producing electrical impulses representative of said Waves, a voice sending means included in said input circuit for producing voice signals in said output circuit, means including said output circuit for transmitting said electrical impulses to said recorder, and means operable invresponse to electrical impulses applied to said input circuit for preventing transfer to said output circuit of said voice signals and of additional impulses,

7. In a system for transmitting seismic signals and voice signals, the combination of a thermionic tube having an input circuit including a control electrode and an output circuit in which signals applied to said controlelectrode are reproduced, means for applying voice signals and an impulse indicative of the instant of creation of seismic waves to said control electrode, and means operable immediately after application of said impulse to said electrode for preventing reproduction in said output circuit of signals and impulses later applied to said control electrode.

8. In a system for transmitting seismic signals and voice signals, the combination of an electrical translating device having an input circuit and an output circuit in which signals applied to said input circuit are reproduced, a geophone operable by seismic waves for producing electrical signals in said input circuit representative of said waves, means for producing voice signals in'said input circuit, and means operable automatically after application 'of initial signals by said geophone to said input circuit for prevent-` 'ing appearance in said output circuit of additional geophone signals and of voice signals.

9. In` a system for transmitting seismic signals andA voice signals, the combination of an' electrical translating device having an input circuit and an output circuit in which signals applied to said input circuit are reproduced, means for applying to said input circuit an electrical signal coincidentally with generation of seismic waves, a geophone operable by said seismic waves for producing an electrical signal in said input circuit representative of rst reception by said geophone of said waves, means for producing voice signals in said input circuit, and means operable automatically after application to said input circuit of said rst two signals for preventc said input circuit representative of flrst reception by said geophone of. said waves, means for producing voice signals in said input circuit, means operable automatically after application to said input circuit of several geophone signals for preventing appearance i said output circuit of further signals applied to said input circuit, a recorder, and means including said output circuit and said channel for applying said impulse and'.

said geophone signal to said recorder.

11. In a system for transmitting seismic 'signals and voice signals over a single transmission channel, the combination of an electrical translating device having an input circuit and an output circuit including said channel in which signals applied to said input circuit are reproduced, a geophone operable by seismic waves for producing electrical signals in said input circuit representative of reception by said .geophone of said waves, means for applying' to said input circuit an electrical impulse coincidentally with generation of said seismic waves. means for producing voice signals in said input circuit, means operable automatically after application to said input circuit of several geophone signals for preventing appearance in said output circuit of further signals applied to said input circuit, and manually operable means for restoring operation of said translating device, whereby voice signals produced in said input circuit may again appear in said output circuit.

12. In a system having a seismic wave generating means and an uphole geophone ata sending point, at least one geophone and a recorder at a receiving point spacedv a substancircuit and operable in response tov arrival of y seismic waves vat said uphole geophone for producing electrical impulses, a voice sending means included in said input circuit, means including said' output circuit for transmitting voice signals and said electrical impulses to said receiving point, means operable in response to electrical impulses applied to said input circuit -for biasing said amplifier to prevent transfer to its output circuit of all signals applied to the input circuit of said amplifier, manually operable means for removing the bias applied by said last-mentioned means andfor restoring normal operation of said amplifier, and means including said output circuit and said single transmission channel for applying to said recorder said rst-named impulse and said uphole geophone impulses.

13. In a system having a seismic wave generating means and an uphole geophone at a, shotpoint, a recorder and at least one geophone of a spread at a recording location and a transmission channel interconnecting the shotpoint and recording location, the combination of an amplier at said shotpoint having an input circuit and an output circuit including said channel,

`means included in said input circuit for producvapplied to said input circuit for rendering said amplier inoperative thereby to prevent transfer to its output circuit of signals and impulses applied to its input circuit, said last-mentioned means having no eiect on reception at said shotpoint of signals from said recording location.

14. In a system for producing and transmit- .ting seismic signals, means for producing a voltage impulse coincidentally with the creation of seismic waves, a recorder, a transmission channel for 'transmitting signals to said recorder and including a repeater tubehaving an anode, a cathode, and a control grid, means for impressing said last-mentioned voltage impulse upon the grid tial vdistance therefrom and a single transmis-v sion channel interconnecting said sending and incident withinitiation by the generating meansv of seismic waves, means included in said input of ysaid repeater tube for transmission to said recorder as the time break, means including a geophone for detecting andv amplifying seismic waves received thereby and for applying them to the grid of said repeater tube, a control tube having the characteristic of flow of anode current once the grid loses control, means forapplying voice signals to said repeater tube, and means operable by a signal from said geophone for causing said grid of said control tube 'to lose control, said control tube having an output circuit including a'current responsive biasing means operable after a time delay negatively to bias said' repeater tube to prevent transmission ofv further y signals over said channel, and means manually operable to again render said grid of said control tube eilective to'prevent ilow of anode cur rent and to restore operation of said repeater tube for transmission of signals over said channel.

EARLEY M. SHOOK. ROBERT W. OLSON.l 

